Synovitis and the risk of knee osteoarthritis: the MOST Study

OBJECTIVE

To identify the independent relation of synovitis with incident radiographic knee osteoarthritis (OA) after adjusting for other structural factors known to cause synovitis.

DESIGN

We examined MRIs from knees that developed incident radiographic OA from the Multicenter Osteoarthritis Study (MOST) and compared these case knees with controls that did not develop OA. We examined baseline MRIs for knees developing OA at any time up to 84 months follow-up. We scored lesions in cartilage, meniscus, bone marrow and synovitis. Synovitis scores were summed (0-9) across three regions, suprapatellar, infrapatellar and intercondylar region, each of which was scored 0-3. After bivariate analyses examining each factor's association with incidence, we carried out multivariable regression analyses adjusting for age, sex, BMI, alignment and cartilage and meniscal damage.

RESULTS

We studied 239 case and 731 control knees. In bivariate analyses, cartilage lesions, meniscal damage, synovitis and bone marrow lesions were all risk factors for OA. After multivariable analyses, synovitis was associated with incident OA. A higher synovitis score increased the risk of incident OA (adjusted OR per unit increase 1.1; (95% CI 1.0, 1.2, P = .02)), but increased risk was associated only with synovitis scores of ≥3 (adjusted OR 1.6; 95% CI 1.2, 2.1, P = .003).

CONCLUSIONS

Synovitis, especially when there is a substantial volume within the knee, is an independent cause of OA.

Structural correlates of pain in joints with osteoarthritis

OBJECTIVE

To describe the insights on the epidemiology of pain-structure association and the ramifications of these studies for clinical trials.

DESIGN

Narrative review summarizing the pertinent literature in this area, summarizing some of the methodologic challenges inherent and proposing some research initiatives to further understanding of this complex science.

RESULTS

The predominant symptom in most patients presenting with osteoarthritis (OA) is pain. Over recent years a number of imaging based studies have narrowed the discord between structural findings on imaging and symptoms. The interpretation of pain in OA is still enigmatic and difficult to deal with both for clinicians and scientists.

CONCLUSIONS

We would envisage that over the next few years many of the pressing questions pertaining to research into the structure pain relationship will continue to be addressed. With this, we can expect clinically appropriate therapeutic advance.

Cartilage loss occurs in the same subregions as subchondral bone attrition: a within-knee subregion-matched approach from the Multicenter Osteoarthritis Study

OBJECTIVE

By magnetic resonance imaging (MRI), subchondral bone attrition (SBA) can be seen in early osteoarthritis (OA), but the significance of this is unknown. We therefore evaluated whether SBA was associated with cartilage loss within the same subregion of the knee.

METHODS

The Multicenter Osteoarthritis Study is a cohort of individuals who have or are at high risk for knee OA. At baseline and 30 months, participants' knee MRIs were graded using the Whole-Organ Magnetic Resonance Imaging Score in the 10 subregions of the tibiofemoral joint for cartilage morphology and SBA. We conducted analyses within a knee to eliminate between-person confounding, using an M:N (cases:controls) matched case-control approach with the 10 subregions of a person's knee forming a matched set. Cases within a knee were defined as subregions with cartilage loss, while controls were subregions in that same knee without cartilage loss. We evaluated the association of cartilage loss over 30 months with the presence of baseline SBA in the same subregion within that knee using conditional logistic regression.

RESULTS

SBA was associated with an odds ratio of 7.5 (95% confidence interval 5.6-9.9, P < 0.0001) for cartilage loss in the same subregion compared with subregions without any baseline SBA in our sample of 459 knees from participants, 64% of whom were women, with a mean age of 63 years and a mean body mass index of 30.5 kg/m(2).

CONCLUSION

SBA is strongly associated with cartilage loss within the same subregion of a knee. SBA may directly influence overlying cartilage loss or serve as a marker of an area undergoing great compressive stress and in which cartilage loss is inevitable.

Pre-radiographic MRI findings are associated with onset of knee symptoms: the most study

OBJECTIVE

Magnetic resonance imaging (MRI) has greater sensitivity to detect osteoarthritis (OA) damage than radiographs but it is uncertain which MRI findings in early OA are clinically important. We examined MRI abnormalities detected in knees without radiographic OA and their association with incident knee symptoms.

METHOD

Participants from the Multicenter Osteoarthritis Study (MOST) without frequent knee symptoms (FKS) at baseline were eligible if they also lacked radiographic features of OA at baseline. At 15 months, knees that developed FKS were defined as cases while control knees were drawn from those that remained without FKS. Baseline MRIs were scored at each subregion for cartilage lesions (CARTs); osteophytes (OST); bone marrow lesions (BML) and cysts. We compared cases and controls using marginal logistic regression models, adjusting for age, gender, race, body mass index (BMI), previous injury and clinic site.

RESULTS

36 case knees and 128 control knees were analyzed. MRI damage was common in both cases and controls. The presence of a severe CART (P=0.03), BML (P=0.02) or OST (P=0.02) in the whole knee joint was more common in cases while subchondral cysts did not differ significantly between cases and controls (P>0.1). Case status at 15 months was predicted by baseline damage at only two locations; a BML in the lateral patella (P=0.047) and at the tibial subspinous subregions (P=0.01).

CONCLUSION

In knees without significant symptoms or radiographic features of OA, MRI lesions of OA in only a few specific locations preceded onset of clinical symptoms and suggest that changes in bone play a role in the early development of knee pain. Confirmation of these findings in other prospective studies of knee OA is warranted.

Varus thrust during walking and the risk of incident and worsening medial tibiofemoral MRI lesions: the Multicenter Osteoarthritis Study

OBJECTIVE

To determine the association of varus thrust during walking to incident and worsening medial tibiofemoral cartilage damage and bone marrow lesions (BMLs) over 2 years in older adults with or at risk for osteoarthritis (OA).

METHOD

Subjects from the Multicenter Osteoarthritis Study (MOST) were studied. Varus thrust was visually assessed from high-speed videos of forward walking trials. Baseline and two-year MRIs were acquired from one knee per subject and read for cartilage loss and BMLs. Logistic regression with generalized estimating equations was used to estimate the odds of incident and worsening cartilage loss and BMLs, adjusting for age, sex, race, body mass index (BMI), and clinic site. The analysis was repeated stratified by varus, neutral, and valgus alignment.

RESULTS

1007 participants contributed one knee each. Varus thrust was observed in 29.9% of knees. Knees with thrust had 2.17 [95% CI: 1.51, 3.11] times the odds of incident medial BML, 2.51 [1.85, 3.40] times the odds of worsening medial BML, and 1.85 [1.35, 2.55] times the odds of worsening medial cartilage loss. When stratified by alignment, varus knees also had significantly increased odds of these outcomes.

CONCLUSION

Varus thrust observed during walking is associated with increased odds of incident and worsening medial BMLs and worsening medial cartilage loss. Increased odds of these outcomes persist in varus-aligned knees.

Does cartilage volume or thickness distinguish knees with and without mild radiographic osteoarthritis? The Framingham Study

OBJECTIVES

To examine whether the quantity of cartilage or semiquantitative scores actually differ in knees with mild radiographic osteoarthritis compared with knees without osteoarthritis.

METHODS

Framingham Osteoarthritis Study participants had knee tibiofemoral magnetic resonance imaging-based measurements of cartilage. Using three-dimensional FLASH-water excitation sequences, cartilage volume, thickness and subregional cartilage thickness were measured and cartilage scored semiquantitatively (using the whole-organ magnetic resonance imaging score; WORMS). Using weight-bearing radiographs, mild osteoarthritis was defined as Kellgren/Lawrence (K/L) grade 2 and non-osteoarthritis as K/L grade 0. Differences between osteoarthritis and non-osteoarthritis knees in median cartilage measurements were tested using the Wilcoxon rank sum test.

RESULTS

Among 948 participants (one knee each), neither cartilage volume nor regional thickness were different in mild versus non-osteoarthritis knees. In mild osteoarthritis, cartilage erosions in focal areas were missed when cartilage was quantified over large regions such as the medial tibia. For some but not all subregions of cartilage, especially among men, cartilage thickness was lower (p<0.05) in mild osteoarthritis than non-osteoarthritis knees. Because semiquantitative scores captured focal erosions, median WORMS scores were higher in mild osteoarthritis than non-osteoarthritis (all p<0.05). In moderate/severe osteoarthritis (K/L grades 3 or 4), osteoarthritis knees had much lower cartilage thickness and higher WORMS scores than knees without osteoarthritis.

CONCLUSIONS

In mild osteoarthritis, the focal loss of cartilage is missed by quantitative measures of cartilage volume or thickness over broad areas. Regional cartilage volume and thickness (eg, medial tibia) are not different in mild osteoarthritis versus non-osteoarthritis. Subregional thickness may be decreased in mild osteoarthritis. Semiquantitative scoring that assesses focal cartilage damage differentiates mild osteoarthritis from non-osteoarthritis.

Towards prevention of post-traumatic osteoarthritis: report from an international expert working group on considerations for the design and conduct of interventional studies following acute knee injury

OBJECTIVE

There are few guidelines for clinical trials of interventions for prevention of post-traumatic osteoarthritis (PTOA), reflecting challenges in this area. An international multi-disciplinary expert group including patients was convened to generate points to consider for the design and conduct of interventional studies following acute knee injury.

DESIGN

An evidence review on acute knee injury interventional studies to prevent PTOA was presented to the group, alongside overviews of challenges in this area, including potential targets, biomarkers and imaging. Working groups considered pre-identified key areas: eligibility criteria and outcomes, biomarkers, injury definition and intervention timing including multi-modality interventions. Consensus agreement within the group on points to consider was generated and is reported here after iterative review by all contributors.

RESULTS

The evidence review identified 37 studies. Study duration and outcomes varied widely and 70% examined surgical interventions. Considerations were grouped into three areas: justification of inclusion criteria including the classification of injury and participant age (as people over 35 may have pre-existing OA); careful consideration in the selection and timing of outcomes or biomarkers; definition of the intervention(s)/comparator(s) and the appropriate time-window for intervention (considerations may be particular to intervention type). Areas for further research included demonstrating the utility of patient-reported outcomes, biomarkers and imaging outcomes from ancillary/cohort studies in this area, and development of surrogate clinical trial endpoints that shorten the duration of clinical trials and are acceptable to regulatory agencies.

CONCLUSIONS

These considerations represent the first international consensus on the conduct of interventional studies following acute knee joint trauma.

Trajectory of cartilage loss within 4 years of knee replacement--a nested case-control study from the osteoarthritis initiative

OBJECTIVE

Knee replacement (KR) represents a clinically important endpoint of knee osteoarthritis (KOA). Here we examine the 4-year trajectory of femoro-tibial cartilage thickness loss prior to KR vs non-replaced controls.

METHODS

A nested case-control study was performed in Osteoarthritis Initiative (OAI) participants: Cases with KR between 12 and 60 month (M) follow-up were each matched with one control (without KR through 60M) by age, sex, and baseline radiographic stage. Femoro-tibial cartilage thickness was measured quantitatively using magnetic resonance imaging (MRI) at the annual visit prior to KR occurrence (T0), and at 1-4 years prior to T0 (T-1 to T-4). Cartilage loss between cases and controls was compared using paired t-tests and conditional logistic regression.

RESULTS

One hundred and eighty-nine knees of 164 OAI participants [55% women; age 64 ± 8.7; body mass index (BMI) 29 ± 4.5] had KR and longitudinal cartilage data. Comparison of annualized slopes of change across all time points revealed greater loss in the central medial tibia (primary outcome) in KRs than in controls [94 ± 137 vs 55 ± 104 μm; P = 0.0017 (paired t); odds ratio (OR) 1.36 (95% confidence interval (CI): 1.08-1.70)]. The discrimination was stronger for T-2 → T0 [OR 1.61 (1.33-1.95), n = 127] than for T-1 → T0, and was not statistically significant for intervals prior to T-2 [i.e., T-4 → T-2, OR 0.97 (0.67-1.41), n = 60]. Results were similar for total medial femoro-tibial cartilage loss (secondary outcome), and when adjusting for pain and BMI.

CONCLUSIONS

In knees with subsequent replacement, cartilage loss accelerates in the 2 years, and particularly in the year prior to surgery, compared with controls. Whether slowing this cartilage loss can delay KR remains to be determined.

Osteoarthritis year in review 2019: imaging

OBJECTIVE

To provide a narrative review of original articles on osteoarthritis (OA) imaging published between April 1, 2018 and March 30, 2019.

METHODS

All original research articles on OA imaging published in English between April 1, 2018 and March 30, 2019 were identified using a PubMed database search. The search terms of "Osteoarthritis" or "OA" were combined with the search terms "Radiography", "X-Rays", "Magnetic Resonance Imaging", "MRI", "Ultrasound", "US", "Computed Tomography", "Dual Energy X-Ray Absorptiometry", "DXA", "DEXA", "CT", "Nuclear Medicine", "Scintigraphy", "Single-Photon Emission Computed Tomography", "SPECT", "Positron Emission Tomography", "PET", "PET-CT", or "PET-MRI". Articles were reviewed to determine relevance based upon the following criteria: 1) study involved human subjects with OA or risk factors for OA and 2) study involved imaging to evaluate OA disease status or OA treatment response. Relevant articles were ranked according to scientific merit, with the best publications selected for inclusion in the narrative report.

RESULTS

The PubMed search revealed a total of 1257 articles, of which 256 (20.4%) were considered relevant to OA imaging. Two-hundred twenty-six (87.1%) articles involved the knee joint, while 195 (76.2%) articles involved the use of magnetic resonance imaging (MRI). The proportion of published studies involving the use of MRI was higher than previous years. An increasing number of articles were also published on imaging of subjects with joint injury and on deep learning application in OA imaging.

CONCLUSION

MRI and other imaging modalities continue to play an important role in research studies designed to better understand the pathogenesis, progression, and treatment of OA.

Characteristics of acute groin injuries in the adductor muscles: A detailed MRI study in athletes

Acute adductor injuries account for the majority of acute groin injuries; however, little is known about specific injury characteristics, which could be important for the understanding of etiology and management of these injuries. The study aim was to describe acute adductor injuries in athletes using magnetic resonance imaging (MRI). Male athletes with acute groin pain and an MRI confirmed acute adductor muscle injury were prospectively included. MRI was performed within 7 days of injury using a standardized protocol and a reliable assessment approach. 156 athletes presented with acute groin pain of which 71 athletes were included, median age 27 years (range 18-37). There were 46 isolated muscle injuries and 25 athletes with multiple adductor injuries. In total, 111 acute adductor muscle injuries were recorded; 62 adductor longus, 18 adductor brevis, 17 pectineus, 9 obturator externus, 4 gracilis, and 1 adductor magnus injury. Adductor longus injuries occurred at three main injury locations; proximal insertion (26%), intramuscular musculo-tendinous junction (MTJ) of the proximal tendon (26%) and the MTJ of the distal tendon (37%). Intramuscular tendon injury was seen in one case. At the proximal insertion, 12 of 16 injuries were complete avulsions. This study shows that acute adductor injuries generally occur in isolation from other muscle groups. Adductor longus is the most frequently injured muscle in isolation and in combination with other adductor muscle injuries. Three characteristic adductor longus injury locations were observed on MRI, with avulsion injuries accounting for three-quarters of injuries at the proximal insertion, and intramuscular tendon injury was uncommon.

Correlations of Medial Joint Space Width on Fixed-Flexed Standing Computed Tomography and Radiographs With Cartilage and Meniscal Morphology on Magnetic Resonance Imaging

OBJECTIVE

To assess whether medial tibiofemoral joint space width (JSW) on 3-dimensional (3-D) standing computed tomography (SCT) correlates more closely with magnetic resonance imaging cartilage morphology (CM) and meniscal scores than does radiographic 2-D JSW.

METHODS

Participants in the Multicenter Osteoarthritis Study, who had standing fixed-flexion posteroanterior knee radiographs, were recruited. Medial tibiofemoral 3-D JSW on SCT and 2-D JSW on fixed-flexion radiographs were compared with medial tibiofemoral cartilage and meniscal morphology using the Whole-Organ Magnetic Resonance Imaging Score (WORMS). Associations between the area of the articular surface with 3-D JSW <2.5 mm on SCT, radiographic minimal 2-D JSW, and the WORMS-CM and meniscal scores were assessed using Spearman's rho.

RESULTS

For the 19 participants included (33 knees), mean ± SD age was 66.9 ± 5.4 years, body mass index was 29.5 ± 4.4 kg/m(2) , 42.1% of participants were female, and the Kellgren/Lawrence grades were 0 (21.2%), 1 (36.4%), 2 (18.2%), and 3 (24.2%). The articular surface area with 3-D JSW <2.5 mm on SCT correlated with WORMS-CM scores for the central medial tibia (rs  = 0.84, P < 0.001), central medial femur (rs  = 0.60, P < 0.007), and posterior medial meniscal tear (rs  = 0.39, P < 0.026), as did other cut points for 3-D JSW. Correlations with radiographic minimal 2-D JSW were -0.66, -0.52, and -0.40, respectively, differing from SCT only for tibial cartilage (P = 0.001).

CONCLUSION

Greater surface area with a low JSW, measured by SCT, correlates more strongly with the severity of tibial cartilage lesions, while correlating with medial femoral cartilage and meniscal damage to a similar extent as radiographic minimal JSW. SCT may enable valid stratification of participants in clinical trials, through quickly and inexpensively characterizing osteoarthritis features.

Thigh muscle cross-sectional areas and strength in knees with early vs knees without radiographic knee osteoarthritis: a between-knee, within-person comparison

OBJECTIVE

To compare cross-sectional and longitudinal side-differences in thigh muscle anatomical cross-sectional areas (ACSAs), muscle strength, and specific strength (strength/ACSA), between knees with early radiographic change vs knees without radiographic knee osteoarthritis (RKOA), in the same person.

DESIGN

55 (of 4796) Osteoarthritis Initiative (OAI) participants fulfilled the inclusion criteria of early RKOA in one limb (definite tibiofemoral osteophytes; no radiographic joint space narrowing [JSN]) vs no RKOA (no osteophyte; no JSN) in the contralateral limb. ACSAs of the thigh muscles and quadriceps heads were determined using axial MRIs at 33%/30% femoral length (distal to proximal). Isometric extensor and flexor muscle strength were measured (Good Strength Chair). Baseline quadriceps ACSA and extensor (specific) strength represented the primary analytic focus, and 2-year changes of quadriceps ACSAs the secondary focus.

RESULTS

No statistically significant side-differences in quadriceps (or other thigh muscle) ACSAs, muscle strength, or specific strength were observed between early RKOA vs contralateral limbs without RKOA (P ≥ 0.44), neither in men nor in women. The 2-year reduction in quadriceps ACSA in limbs with early RKOA was -0.9 ± 6% (mean ± standard deviation) vs -0.5 ± 6% in limbs without RKOA (statistical difference P = 0.85).

CONCLUSION

Our results do not provide evidence that early unilateral radiographic changes, i.e., presence of osteophytes, are associated with cross-sectional or longitudinal differences in quadriceps muscle status compared with contralateral knees without RKOA. At the stage of early unilateral RKOA there thus appears to be no clinical need for countervailing a potential dys-balance in quadriceps ACSAs and strength between both knees.

Imaging following acute knee trauma

Joint injury has been recognized as a potent risk factor for the onset of osteoarthritis. The vast majority of studies using imaging technology for longitudinal assessment of patients following joint injury have focused on the injured knee joint, specifically in patients with anterior cruciate ligament injury and meniscus tears where a high risk for rapid onset of post-traumatic osteoarthritis is well known. Although there are many imaging modalities under constant development, magnetic resonance (MR) imaging is the most important instrument for longitudinal monitoring after joint injury. MR imaging is sensitive for detecting early cartilage degeneration and can evaluate other joint structures including the menisci, bone marrow, tendons, and ligaments which can be sources of pain following acute injury. In this review, focusing on imaging following acute knee trauma, several studies were identified with promising short-term results of osseous and soft tissue changes after joint injury. However, studies connecting these promising short-term results to the development of osteoarthritis were limited which is likely due to the long follow-up periods needed to document the radiographic and clinical onset of the disease. Thus, it is recommended that additional high quality longitudinal studies with extended follow-up periods be performed to further investigate the long-term consequences of the early osseous and soft tissue changes identified on MR imaging after acute knee trauma.

Loss of anterior cruciate ligament integrity and the development of radiographic knee osteoarthritis: a sub-study of the osteoarthritis initiative

INTRODUCTION

The aim of this study was to determine whether loss of ACL integrity in an older cohort precedes the onset of radiographic OA (ROA).

METHODS

Participants in this nested case-control study were selected from the Osteoarthritis Initiative (OAI) study who had risk factors for OA development but did not have ROA (Kellgren-Lawrence grading (KLG) of 0 or 1) in both knees at baseline. The MRIs were assessed for the presence of ACL tears. Case knees were defined by the development of ROA on knee radiographs between the 12 and 48 month visits. Their radiographs were assessed at P0 (time of onset of radiographic knee OA), 1 year prior to P0 (P-1) and at baseline. Controls were selected from amongst those who did not develop incident ROA and were matched to cases.

RESULTS

355 persons who developed ROA were matched to 355 controls. No relationship between loss of ACL integrity and incident ROA was found at any assessment time point. Odds ratios (OR) for baseline, 1 year prior to incident ROA (P1) and at point of occurrence of incident ROA (P0) were 2.00 (0.66-6.06), 2.5 (0.76-8.24) and 2.75 (0.85-8.88) respectively. A significant risk of incident ROA was found in participants who had a history of knee injury with an OR of 1.51 (1.05-2.16).

CONCLUSION

Loss of ACL integrity does not confer a significantly increased risk of incident ROA in an older adult cohort. In contrast, a history of knee injury was associated with an increased risk of incident ROA.

[Acute, traumatic versus chronic cartilage lesions as terms of a medical expert's opinion]

AIM

Have chondral lesions been found in the course of an articular injury? Are these lesions of traumatic or degenerative origin? Is it possible to differentiate traumatic from pre-existing pathology with the help of history, clinical findings and imaging features? The answers to these questions are of paramount importance in the setting of legal expert assessment.

METHOD

The diagnosis of an acute traumatic chondral injury is based on arthroscopic and/or MRI findings. MRI is the diagnostic method of choice in a suspected isolated chondral injury.

RESULTS

The method yields high accuracy in detecting chondral and osteochondral lesions. The MRI finding of a concomitant subchondral bone contusion ("bone bruise") adjacent to a cartilage lesion helps in the diagnosis of acute chondral lesions. Traumatic bone marrow alterations regress in most cases over the course of 6 months. For this reason the initial MRI should be performed within 1 to 6 weeks after trauma. A follow-up study should be undertaken not prior to 3 months after injury. Osteoarthritic cartilage lesions show a distinct regional pattern on MRI usually affecting the weight-bearing regions. In advanced stages, regularly concomitant osseous reactions such as osteophytes, subchondral sclerosis and bone attrition are observed. Subchondral bone marrow lesions in osteoarthritis show a tendency to progress.

CONCLUSION

The direct inspection and probing of the joint during arthroscopy allows for a detailed assessment of the chondral surface and the diagnosis of possible cartilage softening. An arthroscopic differentiation between acute traumatic chondral lesions and chronic cartilage alterations is possible in most cases within the first 6 to 12 weeks after injury.

7th International Workshop on Osteoarthritis Imaging report: "imaging in OA--now is the time to move ahead"

The 7th Osteoarthritis Research Society International (OARSI) International Workshop on Osteoarthritis Imaging was held in Reykjavik, Iceland, from July 9-12, 2014; attracting attendees from academia, pharmaceutical and Magnetic resonance imaging (MRI) industries, as well as a large number of young investigators. The Workshop program consisted of six modules, including imaging in osteoarthritis (OA), imaging and pain in OA, new techniques in imaging, risk factors and structural outcomes, anti-nerve growth factor (a-NGF) therapy, and joint replacement. A wealth of data was presented from OA researchers from all over the world and participants gained insightful knowledge on up-to-date research work focusing on imaging of OA. This paper presents a summary of the salient points from the workshop.

CONCLUSIONS

Identifying the appropriate imaging modality and parameters will be critical for ensuring responsive, reproducible and reliable outcomes for clinical trials. Continued efforts from the OA research community are needed to establish the most effective use of imaging in OA clinical trials, including anti-NGF therapy and joint replacement trials, and to validate newer imaging techniques such as compositional MRI for use in the future clinical trials.

POS0177 HETEROGENOUS CARTILAGE DAMAGE SEEN ON MRI AMONG KNEES WITH KELLGREN-LAWRENCE 2 & 3 OSTEOARTHRITIS: WHAT ARE THE IMPLICATIONS FOR CLINICAL TRIALS?

Background

The most recent update of the Global Burden of Disease figures (GBD 2013) estimated that 242 million people were living in the world with symptomatic and activity-limiting OA of the hip and/or knee. Many potential disease-modifying osteoarthritis drugs (DMOADs) have been investigated, but to date no DMOADs that slow or stop disease progression have been approved by the Food and Drug Administration (FDA) or the European Medicines Agency (EMA). A potential reason for the lack of demonstrated efficacy may be reliance on radiographs for defining structural inclusion and exclusion criteria for clinical trials, such as use of joint space width and Kellgren-Lawrence (KL) grade as surrogates for cartilage damage.

Objectives

To estimate the distribution of cartilage damage seen on knee MRI in a sample of knees with radiographic KL 2 and 3 OA that would potentially qualify for a DMOAD trial.

Methods

We selected knees from the Osteoarthritis Initiative (OAI), a longitudinal cohort study of knees with or at risk of developing symptomatic radiographic OA, that met common structural inclusion criteria for DMOAD trial enrollment at OAI baseline: knees with radiographs centrally graded as KL 2 or 3 and medial minimum joint space width (mJSW) ≥ 1.5mm. A musculoskeletal radiologist with 10 years of experience in semi-quantitative MRI assessment scored knee cartilage damage in the medial and lateral tibiofemoral and patellofemoral compartments using WORMS (Whole-Organ Magnetic Resonance Imaging Score). Coronal intermediate weighted (IW) TSE and sagittal fat-suppressed IW TSE sequences on 3T MRI were used. The WORMS cartilage scores, which are based on both the extent and depth of cartilage damage, were collapsed into 4 categories: no cartilage damage (WORMS 0 and 1), focal partial or full-thickness (PT/FT) cartilage damage (WORMS 2 and 2.5), diffuse partial thickness (PT) cartilage damage (WORMS 3 and 4), and diffuse full-thickness (FT) cartilage damage (WORMS 5 and 6). We estimated the prevalence of each category of cartilage damage in KL2 and KL3 knees; 95% confidence intervals (CI) accounted for clustering at the participant-level since some participants contributed two knees to the analysis.

Results

We identified 2,372 participants contributing 3,446 knees with radiographic OA (KL 2 and 3) and medial mJSW ≥ 1.5mm. There were 2,318 KL2 knees and 1,128 KL3 knees. The distribution of cartilage damage in each compartment by KL grade is presented in Table 1. We found no cartilage damage in any compartments in 9.8% (95%CI: 8.5, 11.1) of KL2 knees and 2.0% (95%CI: 1.1, 2.9) of KL3 knees. Cartilage damage was absent in the medial tibiofemoral compartment in 52.4% (95%CI: 50.1, 54.6) of KL2 knees, and 14.4% (95%CI: 12.2, 16.6) of KL3 knees, versus 61% (95%CI: 58.8, 63.2) of KL2 knees and 53.6% (95%CI: 50.4, 56.7) of KL3 knees in the lateral compartment. When medial and lateral compartments were combined, cartilage damage was absent in 34.8% (95%CI: 32.7, 36.9) of the KL2 knees, and 4.3% (95%CI: 3.0, 5.5) of the KL3 knees. Diffuse FT cartilage lesions in the medial compartment were found in 6.1% (95%CI: 5.0, 7.1) of KL2 knees and 42.5% (95%CI: 39.4, 45.6) of KL3 knees.

Conclusion

MRI screening prior to clinical trial enrollment may identify a substantial percentage of knees with normal cartilage, as well as knees with diffuse FT cartilage lesions that may not be responsive to DMOADs, depending on the mode of action of a given pharmacological compound.

Disclosure of Interests

Mohamed Jarraya: None declared, Frank Roemer Shareholder of: Boston Imaging Core Lab, Consultant of: California Institute of Biomedical Research, Erin Ashbeck: None declared, John Lynch: None declared, C. Kent Kwoh Consultant of: Novartis, Regeneron, LG Chem, Kolon Tissue Gene, Avalor, Grant/research support from: Pfizer, Lilly, Cumberland, Ali Guermazi Shareholder of: Stock options in BICL, Consultant of: Pfizer, TissueGene, MerckSerono, Regeneron, Novartis, AstraZeneca

OP0292 CLASSIFICATION OF PSORIATIC ARTHRITIS, SERONEGATIVE RHEUMATOID ARTHRITIS, AND SEROPOSITIVE RHEUMATOID ARTHRITIS USING DEEP LEARNING ON MAGNETIC RESONANCE IMAGING

Background

While MRI evaluation of joints has been primarily used to quantify inflammation at a cross-sectional and longitudinal level, less is known about the potential of MRI in distinguishing different patterns of inflammation in the various forms of arthritis.

Objectives

To evaluate (i) whether deep learning using neural networks can be trained to distinguish between seropositive rheumatoid arthritis (RA+), seronegative RA (RA-), and psoriatic arthritis (PsA) based on structural inflammatory patterns on hand magnetic resonance imaging and (ii) to assess if psoriasis patients with subclinical inflammation fit into such patterns.

Methods

ResNet 3D [1] neural networks were trained to distinguish (i) RA+ vs. PsA, (ii) RA- vs. PsA and (iii) RA+ vs. RA- with respect to hand MRI data. Diagnosis of patients was determined using the following guidelines: ACR/EULAR 2010 [2] for RA and CASPAR [3] for PsA. Results from T1 coronal, T2 coronal, T1 coronal and axial fat suppressed contrast-enhanced (CE) and T2 fat suppressed axial sequences were used. The performance of such trained networks was analyzed by the area-under-the-receiver-operating-characteristic curve (AUROC) with and without imputation of demographic and clinical parameters (Figure 1A). Additionally, the trained networks were applied to psoriasis patients without clinical signs of PsA.

Figure 1.

(A) Neural network combining MR sequences with optional additional clinical data. The prediction for a single case is formed by averaging the prediction of all sequences and the clinical data. (B) Plot of the AUROC for increasing percentages (0.6 – 60%) of training data for the differentiation between RA+ and PsA by the neural network. The light blue area around the dark blue mean indicates the uncertainty measured using a 5-fold cross-validation.

Results

MRI scans from 649 patients (135 RA-, 190 RA+, 177 PsA, 147 psoriasis) were included (Table 1). The AUROC for differentiation between disease entities was 75% (SD 3%) for RA+ vs. PsA, 74% (SD 8%) for RA- vs. PsA, and 67% (6%) for RA+ vs. RA-. All MRI sequences were relevant for classification, however, when deleting CE sequences, the loss of performance was only marginal. The addition of patient-specific data to the networks did not provide significant improvements. Increasing amounts of training data demonstrated improved performance of the networks (Figure 1B). Psoriasis patients were mostly assigned to PsA by the neural networks, suggesting that PsA-like MRI pattern may be present early in the course of psoriatic disease.

Table 1.

Overview of demographic and clinical information.

RA+RA-PsAPsoriasisTotal Number (N)649Number (N)190135177147Age (years), mean±SD56.9±12.660.5±10.356.3±12.049.6±13.8Sex (female/male)126/6493/4292/8571/76BMI (kg/m2), mean±SD26.6±10.527.6 ±9.329.1±11.326.7±6.9Disease duration (years), mean±SD2.6±4.91.3±2.30.8±2.34.2±5.1DAS28, mean±SD3.3±1.33.4±1.23.2±1.3-CRP (mg/L), mean±SD0.9±2.50.7±1.20.5±0.80.5±1.3HAQ, mean±SD0.8±0.60.9±0.80.6±0.60.3±0.4MedicationbDMARD88.46%83.87%81.32%35.01%csDMARD89.52%88.89%80.54%12.28%

Conclusion

Deep learning can be successfully applied to differentiate MRI inflammatory patterns related to RA+, RA-, and PsA. Early changes in psoriasis patients can be recognized by neural networks and are characterized by a pattern that allowed the networks to classify them as PsA.

References

[1]Kensho Hara, Hirokatsu Kataoka, and Yutaka Satoh 2018. Can Spatiotemporal 3D CNNs Retrace the History of 2D CNNs and ImageNet? In Proceedings of the IEEE Conference on Computer Vision and Pattern Recognition (CVPR) (pp. 6546–6555).

[2]Aletaha D, Neogi T et al. 2010 Rheumatoid arthritis classification criteria: an American College of Rheumatology/European League Against Rheumatism collaborative initiative. Arthritis Rheum. 2010 Sep;62(9):2569-81.

[3]Helliwell PS, Taylor WJ. Classification and diagnostic criteria for psoriatic arthritis. Annals of the Rheumatic Diseases 2005;64:ii3-ii8.

Acknowledgements

The study was supported by the Deutsche Forschungsgemeinschaft (DFG-FOR2886 PANDORA and the CRC1181 Checkpoints for Resolution of Inflammation). Additional funding was received by the Bundesministerium für Bildung und Forschung (BMBF; project MASCARA), the ERC Synergy grant 4D Nanoscope, the IMI funded projects HIPPOCRATES and RTCure, the Emerging Fields Initiative MIRACLE of the Friedrich-Alexander-Universität Erlangen-Nürnberg and the Else Kröner-Memorial Scholarship (DS, no. 2019_EKMS.27). Furthermore, infrastructural and hardware support was provided by the d.hip Digital Health Innovation Platform.

Disclosure of Interests

None declared

OP0256 FIBROBLAST ACTIVATION PROTEIN (FAP) PET-CT IMAGING ALLOWS TO DEPICT INFLAMMATORY JOINT REMODELING IN PATIENTS WITH PSORIATIC ARTHRITIS

Background

Psoriatic arthritis (PsA) is characterized by substantial mesenchymal tissue activation in the context of inflammation leading to structural damage. Measuring mesenchymal tissue activation in humans in vivo is challenging but may represent a possibility to detect regions at risk for structural damage. Recently, theranostic ligands have been developed that selectively bind Fibroblast Activation Protein (FAP) and allow recognition of activated mesenchymal cells in vivo. Accumulation of such FAP-based tracers can be visualized by positron-emission tomography (PET) (1).

Objectives

In this study, we analyzed whether FAP tracer-based PET-CT can detect mesenchymal tissue activation in patients with PsA and whether this signal is associated with joint damage.

Methods

120 consecutive PsA patients fulfilling CASPAR criteria and 100 healthy controls without musculoskeletal disease received full-body PET-CT investigation using a 68Ga-labelled FAP inhibitor (68Ga-FAPI-04) tracer, specifically binding FAP. For all visually identified pathological tracer-positive lesions the mean and maximum standardized uptake value (SUV mean, SUV max) was assessed. Tracer uptake was quantified in peripheral and axial joints and correlated to various composite scores of PsA. Hand MRI scans were performed in parallel to assess inflammation and structural lesions. Follow-up 68Ga-FAPI-04 PET-CT scans were obtained in a subset of patients treated with cytokine inhibitors (follow-up between 3-6 months) to assess joint damage over time. In addition, FAP related tissue responses in synovial biopsy samples were evaluated on a molecular level by high-resolution slide RNA-sequencing in a subset of patients.

Results

68Ga-FAPI-04 accumulated at synovial and enthesial sites in patients with PsA compared to healthy controls (p < 0.0001). Active pain in peripheral as well as axial joints as measured on a visual analogue scale highly correlated with an increased 68Ga-FAPI-04 uptake (peripheral pain: R = 0.718, p < 0.0001; back pain: R = 0.875, p < 0.0001). Disease Activity in PSoriatic Arthritis (DAPSA) score also correlated with the SUV mean and SUV max of FAP expression (R = 0.774; p = 0.0001). Increased 68Ga-FAPI-04 uptake at baseline was associated with progression of joint damage 3-6 months later as assessed by PsAMRIS score (R = 0.778, p < 0.0001). Treatment with cytokine inhibitors partially reduced FAP expression which was associated with arrest of joint damage in MRI. In contrast, persistent FAP expression was associated with a rapid progression of joint damage in MRI. Molecular analysis of synovial biopsy samples from FAP+ lesions revealed interactions between FAP+ fibroblasts and T cells, innate lymphoid cells and macrophages, which was correlated to a strong upregulation of NF-kB related pathways fostering cartilage and bone destruction.

Conclusion

Our study presents the first in-human evidence that fibroblast activation correlates with disease progression and joint damage in patients with PsA. FAP related imaging might therefore improve the risk assessment of rapidly emerging joint damage in PsA and open new options of treat-to-target strategies in PsA.

References

[1]Schmidkonz C, Rauber S, Atzinger A, Agarwal R, Gotz TI, Soare A, Cordes M, Prante O, Bergmann C, Kleyer A, Agaimy A, Kuwert T, Schett G, Ramming A, Disentangling inflammatory from fibrotic disease activity by fibroblast activation protein imaging. Ann. Rheum. Dis. 79 (2020), 1485-1491.

Disclosure of Interests

None declared